*Move Zeroes

Given an array nums, write a function to move all 0's to the end of it while maintaining the relative order of the non-zero elements.

For example, given nums = [0, 1, 0, 3, 12], after calling your function, nums should be [1, 3, 12, 0, 0].

Note:

You must do this in-place without making a copy of the array.
Minimize the total number of operations.

Credits:
Special thanks to @jianchao.li.fighter for adding this problem and creating all test cases.

 1 public class Solution {
 2     public void moveZeroes(int[] nums) {
 3         if (nums == null || nums.length == 0) {
 4             return;
 5         }
 6         int numOfNonZero = 0;
 7         for (int i = 0; i < nums.length; i++) {
 8             if (nums[i] != 0) {
 9                swap(i, numOfNonZero, nums);
10                numOfNonZero++;
11             }
12         }
13     }
14     
15     private void swap (int i, int j, int[] nums) {
16         int t = nums[i];
17         nums[i] = nums[j];
18         nums[j] = t;
19     }
20 }

reference: http://blog.welkinlan.com/2015/09/20/move-zeroes-leetcode-java/